Astrophysics > Earth and Planetary Astrophysics

Title:Detectable close-in planets around white dwarfs through late unpacking

Abstract: Although 25%-50% of white dwarfs (WDs) display evidence for remnant planetary
systems, their orbital architectures and overall sizes remain unknown. Vibrant
close-in (~1 Solar radius) circumstellar activity is detected at WDs spanning
many Gyrs in age, suggestive of planets further away. Here we demonstrate how
systems with 4 and 10 closely-packed planets that remain stable and ordered on
the main sequence can become unpacked when the star evolves into a WD and
experience pervasive inward planetary incursions throughout WD cooling. Our
full-lifetime simulations run for the age of the Universe and adopt main
sequence stellar masses of 1.5, 2.0 and 2.5 Solar masses, which correspond to
the mass range occupied by the progenitors of typical present-day WDs. These
results provide (i) a natural way to generate an ever-changing dynamical
architecture in post-main-sequence planetary systems, (ii) an avenue for
planets to achieve temporary close-in orbits that are potentially detectable by
transit photometry, and (iii) a dynamical explanation for how residual
asteroids might pollute particularly old WDs.